Ab-initio molecular dynamics simulation of δ-Bi3YO6

An ab initio study of oxide ion dynamics in type-II Bi3NbO7

“…These linked niobate polyhedra are believed to be responsible for a signicant electronic contribution to total conductivity at low temperatures, perhaps through a polaron hopping mechanism. 6,23 Here, we extend these studies to substitution by a supervalent cation, with special attention to the preferred coordination environment and inuence of the substituting cation. Subvalent substitution of Nb 5+ in Bi 3 NbO 7 increases the nominal vacancy concentration and ionic conductivity, as seen for example in the Bi 3 YO 6 -Bi 3 NbO 7 , 17,18 Bi 3 YbO 6 -Bi 3 NbO 7 20 and Bi 3 ZrO 6.5 -Bi 3 NbO 7 21 pseudo-binary systems.…”

Defect structure in δ-Bi5PbY2O11.5

“…Neutron powder diffraction data were collected on the Polaris diffractometer at the ISIS Facility, Rutherford Appleton Laboratory, on back-scattering (130-160 ), 90 (85-95 ), low-angle (28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42) and very low angle (13)(14)(15) detectors over the respective time of ight ranges 1.0 to 20 ms, 0.8 to 19.2 ms, 0.5 to 20 ms and 2.0 to 18.6 ms. Room temperature data were collected with the sample contained in a cylindrical 7 mm diameter thin walled vanadium can, located in front of the back-scattering detectors, while for elevated temperatures, samples were sealed in a silica tube placed inside an 11 mm diameter thin walled vanadium can. Data were collected at 50 C intervals from 300 C to 700 C. Long data collections of 1000 mA h were made at room temperature, 500 C and 700 C to allow for total scattering analysis.…”

“…34 We have found that the GGA functional offers the best compromise between calculation efficiency and accuracy for these types of systems. 35 The electronion interactions were described by the full potential projector augmented wave (PAW) method, 36 with 5, 6, 4 and 11 valence electrons for Bi, O, Pb and Y (including 4s and 4p states as valence for the latter), respectively. Forces in the system were calculated using the Hellmann-Feynman theorem 37,38 and the kinetic energy was controlled by means of the Nose-Hoover thermostat.…”

“…To avoid the inuence of thermal equilibration on the derived results, the rst 10 ps of the MD simulations were ignored. The time step used was based on the results of our previous studies on related systems, 35,42,43 which showed 10 fs to give equivalent accuracy in calculations compared to shorter time steps, when used with a suitable cut-off energy. Pair distributions, contact distances, coordination numbers and ionic density proles were calculated from the MD simulations by summation over all time steps and all ve different initial random distributions of yttrium/lead cations and oxygen vacancies at each studied temperature.…”

Does the low optical band gap of yellow Bi3YO6 guarantee the photocatalytical activity under visible light illumination?

“…One of them is Bi 3 YO 6 that occurs in the δ-phase even at room temperature [14]. The defect structure, vacancy ordering, and oxygen ion transport in the Bi 3 YO 6 δ-phase were studied using ab initio molecular dynamic, as well as total neutron scattering analysis [15][16][17]. Ionic transport in a material and its defect structure are commonly tested in Bi 3 NbO 7 -Bi 3 YO 6 systems [18,19] and in tungsten-doped Bi 3 YO 6 [20].…”